soc/intel/cannonlake: Allow to configure maximum package C state

Sometimes it's preferable or even necessary (e.g. stability issues) to
limit the maximum package C state. Let's add a devicetree option that
keeps the current behavior if it is left unset.

Change-Id: I0dc254d34f46de4c65cb85cc92e4b7f26618888d
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56661
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/soc/intel/cannonlake/chip.h

@@ -64,6 +64,19 @@ struct soc_intel_cannonlake_config {
 	/* Enable DPTF support */
 	int dptf_enable;
 
+	enum {
+		MAX_PC_DEFAULT	= 0,
+		MAX_PC0_1	= 1,
+		MAX_PC2		= 2,
+		MAX_PC3		= 3,
+		MAX_PC6		= 4,
+		MAX_PC7		= 5,
+		MAX_PC7S	= 6,
+		MAX_PC8		= 7,
+		MAX_PC9		= 8,
+		MAX_PC10	= 9,
+	} max_package_c_state;
+
 	/* Deep SX enable for both AC and DC */
 	int deep_s3_enable_ac;
 	int deep_s3_enable_dc;

src/soc/intel/cannonlake/cpu.c

@@ -55,10 +55,16 @@ static void configure_misc(void)
 	wrmsr(MSR_POWER_CTL, msr);
 }
 
-static void configure_c_states(void)
+static void configure_c_states(const config_t *const cfg)
 {
 	msr_t msr;
 
+	msr = rdmsr(MSR_PKG_CST_CONFIG_CONTROL);
+	if (cfg->max_package_c_state && (msr.lo & 0xf) >= cfg->max_package_c_state) {
+		msr.lo = (msr.lo & ~0xf) | ((cfg->max_package_c_state - 1) & 0xf);
+		wrmsr(MSR_PKG_CST_CONFIG_CONTROL, msr);
+	}
+
 	/* C-state Interrupt Response Latency Control 1 - package C6/C7 short */
 	msr.hi = 0;
 	msr.lo = IRTL_VALID | IRTL_32768_NS | C_STATE_LATENCY_CONTROL_1_LIMIT;
@@ -104,7 +110,7 @@ void soc_core_init(struct device *cpu)
 	setup_lapic();
 
 	/* Configure c-state interrupt response time */
-	configure_c_states();
+	configure_c_states(cfg);
 
 	/* Configure Enhanced SpeedStep and Thermal Sensors */
 	configure_misc();